Neil deGrasse Tyson: Finding Aliens Would Help Us Define Life

Finding alien life would undoubtedly be one of the greatest scientific discoveries of all time, if only because we would finally know we're not alone in the universe. But according to your friendly neighborhood astrophysicist, Neil deGrasse Tyson, this discovery would have a less intuitive but equally revolutionary ramification: it could help us finally come up with a comprehensive definition for life.

As of now, there is not a universally accepted definition for life; rather, it is an ongoing conversation that spans biology, chemistry, genetics, and more. Our current working definition of life is descriptive rather than definitive, mostly because we have only observed life on Earth, so while we can describe life as we know it, biologists can't claim to generate a definition that would encompass any "life" we could encounter. So as of now, an organism qualifies as being "alive" if it has all or most of the factors scientists have observed in life forms, such as homeostasis, growth, reproduction, movement, etc.

The closest thing we have to an all-encompassing definition of life is DNA. All cellular life on Earth has DNA—with the possible exception of viruses, but there is debate within the scientific community as to whether viruses are "alive" or not). And scientists have theorized that life we encounter on other planets could be missing DNA, especially since it's widely believed that early life may have solely used RNA as their genetic material.

If we find life that exists and thrives, and its identity is not encoded with DNA, then it is an entire other genesis. We can extol the virtues of the diversity of life—biodiversity—but in the end, all that life is a sample of one, because it all has DNA in common.

If we were to find alien life, Tyson argues, we would be able to eliminate or confirm factors that are essential to life. As of now, the best we can possibly do is define life on Earth (and even that is questionable). But if we were to find life on other planets, we would be able to compare several different kinds of samples in order to discover which factors all life has in common.

You can't claim to fully understand your sample until you have a diversity of kinds of samples.

The discovery of alien life was always going to be groundbreaking, but if we were able to study it closely, it could help us define life itself.

If in the next 50 years we discover life elsewhere, and analyze it, that will transform biology as no discovery before has.